1. Field of the Invention
This invention relates generally to a thin film magnetic head for use in a magnetic recording apparatus and more particularly to a thin film magnetic head which is formed as a whole by a recording and reproducing transducing head and is provided with a single read-write gap commonly used.
2. Description of the Prior Art
A conventional coil-type magnetic head produces a reproducing output proportional to the running speed of a recording medium. On the other hand, a thin film magnetic head uses a magneto resistance effect and produces a constant reproducing output irrespective of a relative speed between the magnetic head and the recording medium. Therefore a high reproducing output is available even under the condition of a low relative speed. For this reason, recently, thin film magnetic heads of this type have been extensively used in magnetic recording apparatus. However, the thin film magnetic head of the magneto resistance effect type has no recording ability, and therefore in order for the magnetic head to have both recording and reproducing functions, it has been necessary that such a head be combined with a coil-type inductive thin film magnetic head. Such a magnetic head is already known, for example, from Japanese Patent Unexamined Publication Nos. 52-12814 and 61-48116.
In a conventional thin film magnetic head, a lower magnetic layer and an upper magnetic layer both extending straight are disposed in opposed relationship to each other on a substrate. The lower and upper magnetic layers cooperate with a magnetic gap, formed between these magnetic layers, to provide a magnetic circuit. A coil layer is formed in interlinking relation such a chain to the magnetic circuit. The upper magnetic layer is divided into two portions, i.e., front and rear (back) portions, and a magneto resistive element is provided to bridge the front and rear portions.
This conventional thin-film magnetic head has a first yoke formed on a substrate, a second yoke formed so as to constitute a reading and writing gap on one end of the first yoke, a third yoke formed so as to be connected to the first yoke at the other end thereof, a coil formed so as to cross to a magnetic circuit constituted by the first yoke, the second yoke, the third yoke and the writing and reading gap, and a magneto resistive element formed to bridge the second and third yokes.
The operation of this thin film magnetic head will now be described. At the time of recording, recording current flows through the coil layer, so that a recording magnetic field leaks from the magnetic gap to the exterior. The recording onto the recording medium is effected by this magnetic field.
At the time of reproducing, a signal flux generated from the recording medium flows into the magneto resistive element from the magnetic gap via the second yoke. The signal is sensed by variations in resistance of the magneto resistive element. Namely, drive current is applied to the magneto resistive element, and the resistance variation in the magneto resistive element is converted into a voltage, and signal reading is effected.
However, in such a conventional thin film magnetic head, a magnetic resistance is large at a dividing portion between the second yoke and the third yoke. This results in a disadvantage that the recording current required for recording signals on the recording medium is quite large. The increase of the recording current increases the size of a circuit for driving the thin film magnetic head, and therefore this is a factor in the failure to provide a compact or small-size construction of the magnetic recording apparatus. Also, the increase of the recording current raises the temperature of the thin film magnetic head, and therefore this is a factor in the deterioration of the durabilities of the thin film magnetic head and the magnetic recording medium.